A centrifugal fan disclosed in Japanese Patent No. 2940301 includes an electric motor and an impeller coupled to the rotary shaft of the electric motor to rotate therewith. The impeller has a plurality of discharge ports for discharging air sucked through a suction port in a radial direction of the rotary shaft. The suction port is opened in an axial direction of the rotary shaft. The impeller further includes a hub coupled to the rotary shaft and extending in the radial direction of the rotary shaft, a shroud facing an outer peripheral portion of the hub and formed with the suction port at a central portion thereof, and a plurality of blades arranged between the outer peripheral portion of the hub and the shroud at intervals in a direction of rotation of the rotary shaft. Each of the discharge ports is formed between radially outer ends of adjacent two of the blades. Each of the blades includes a curved portion at a corner formed between a negative pressure surface thereof and the shroud in order to reduce noise. The curved portion has a curvature that increases from the suction port toward a corresponding one of the discharge ports. The structure of the centrifugal fan according to the related art, however, has a limit for reducing noise.